The present invention relates generally to wireless networks and more particularly to a radar protection device and method for wireless networks.
Current and projected growth for unlicensed wireless devices operating in a frequency band located at approximately 5 Gigahertz has prompted national and international regulatory bodies to promulgate regulations that ensure that interference with incumbent systems is minimized. Such unlicensed wireless devices generally use packeted data and include, but are not limited to, wireless devices in accordance with the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard. More often than not, such regulations are, in part, due to military and weather radar operations ordinarily conducted within the band. Generally, the operation of more unlicensed devices within the band increases the opportunity for interference and raises the noise floor of the band, potentially compromising the operational performance of military and weather radar systems.
For instance, both the European Telecommunications Standards Institute (ETSI) and the Federal Communications Commission (FCC) have published requirements for radio local area network (RLAN) devices that operate in the Unlicensed National Information Infrastructure (U-NII) frequency bands between 5.250–5.350 and 5.470–5.725 Gigahertz. Further, the devices are required to employ a mechanism that allows the devices to share the spectrum with radar operations, notably military and weather radar operations, in such a way that the devices do not interfere with radar operations.
Short of the required sharing of the spectrum, one approach reports a measurement summary in a radio communications system. More specifically, once a mobile station within a system is tuned to a selected frequency range, a measurement is made of communications energy. If communications energy is measured or detected, the energy is decoded to determine whether the communications energy contains packeted data. If packeted data is detected, further analysis of the data packet is conducted to determine whether the packeted data is in accordance with the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard. If it is determined that the packeted data is 802.11 packeted data, a measurement summary field is populated with a value indicating the frequency range to which the mobile station is tuned. Otherwise, an indication is made that 802.11 packeted data is not being communicated on the frequency range to which the mobile station is tuned. The approach uses a rather complex delay correlation method for such determinations. Although this approach reports a measurement summary for a mobile station inclusive of whether or not communicated energy on a particular frequency is 802.11 packeted data, the approach fails to provide a radar protection system for wireless devices that allows the co-existence of a wireless network with radar systems.
However, another approach does allow the co-existence of a wireless network with radar systems. More specifically, this approach provides radar detection and dynamic frequency selection for wireless local area networks. Further, this approach includes a radar detection process that performs a frequency domain analysis of an incoming signal to derive phase and magnitude information, the output of which is binned into 52 bins of 300 kilohertz. The bins are analyzed to identify and distinguish among different types of radar such as continuous wave tone radar and chirping radar in which the pulses are swept across a frequency range. With radar, the power is typically concentrated in one of the bins, or at a specific frequency.
This approach also provides analysis of a packet to determine whether there are any spikes within the packet above a certain threshold, as a spike might indicate a radar signal. The amplitude and duration, i.e., pulse width, of the spike is analyzed to determine whether or not the spike is indicative of a radar signal. Spikes within the packet may be time-stamped so that the spike can be treated as a new or separate event.
This approach also determines the period of a signal once a particular event is determined to be a radar signal through a frequency domain analysis of the length and magnitude of the event. Similarly, a frequency domain analysis is used to determine the period of a signal.
Particularly, this approach uses the forgoing radar detection process at an access point, and if the access point detects the presence of a radar signal, the access point changes channels. Despite providing a radar protection system for wireless devices that allows the co-existence of a wireless network with radar systems, the radar detection process associated with this approach is of limited utility. Foremost, the use of Fast Fourier Transform, Discrete Fourier Transform, or time domain analysis is particularly burdensome. All of these types of analysis require significant computational and processing capabilities. Moreover, such processing can take a considerable amount of time. Further, capabilities inherent in current access points are generally insufficient to allow the use of such types of analysis. Therefore, many existing access points are not capable of using analysis processes associated with this approach.
Thus, there exists a need for a radar protection device and method that addresses the regulatory requirements and allows the co-existence of a wireless network with radar systems.